A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
Discovery of a pulse-phase-transient cyclotron line in the X-ray pulsar Swift J1808.4-1754 and identification of an optical companion
Tekijät: Salganik Alexander, Tsygankov Sergey S, Lutovinov Alexander A, Djupvik Anlaug A, Karasev Dmitr I, Molkov Sergey V
Kustantaja: OXFORD UNIV PRESS
Julkaisuvuosi: 2022
Journal: Monthly Notices of the Royal Astronomical Society
Tietokannassa oleva lehden nimi: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Lehden akronyymi: MON NOT R ASTRON SOC
Vuosikerta: 514
Numero: 2
Aloitussivu: 2707
Lopetussivu: 2715
Sivujen määrä: 9
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stac1462
Verkko-osoite: https://academic.oup.com/mnras/article/514/2/2707/6595324
Rinnakkaistallenteen osoite: https://arxiv.org/abs/2205.12140
In this work, the temporal and spectral properties of the poorly studied X-ray pulsar Swift J1808.4-1754 were investigated in the 0.8-79 keV energy range based on the data from the NuSTAR and Swift observatories collected during the 2014 outburst. Strong pulsations with a period of 909.73 +/- 0.03 s were detected in the source light curve, with the pulsed fraction demonstrating a non-monotonic dependence on the energy with a local minimum around 17-22 keV. Phase lags in one of the pulse profile components, reaching the maximal value approximately at the same energy, were discovered. The pulse phase-averaged spectrum of the source has a power-law shape with an exponential cutoff at high energies, which is typical of X-ray pulsars. Pulse phase-resolved spectroscopy revealed the presence of a pulse-phase-transient cyclotron absorption line at similar to 21 keV, allowing us to estimate the neutron star magnetic field of 2.4 x 10(12) G. This makes Swift J1808.4-1754 a member of very small family of X-ray pulsars with a pulse-phase-transient cyclotron line in a narrow phase range. The data from the Nordic Optical Telescope allowed us to study the properties of the infrared companion in the system and to conclude that most probably it is a Be-type star located at a distance of 5-8 kpc.
